;;;; A version of the TAK function that uses continuations
(define (ctak x y z)
  (call-with-current-continuation
   (lambda (k)
     (ctak-aux k x y z))))

(define (ctak-aux k x y z)
  (cond ((not (< y x)) (k z))
        (else (call-with-current-continuation
               (ctak-aux
                k
                (call-with-current-continuation
                 (lambda (k) (ctak-aux k (- x 1) y z)))
                (call-with-current-continuation
                 (lambda (k) (ctak-aux k (- y 1) z x)))
                (call-with-current-continuation
                 (lambda (k) (ctak-aux k (- z 1) x y))))))))

(define (id x) x)

(define (mb-test r x y z)
  (if (zero? r)
      (ctak x y z)
      (id (mb-test (- r 1) x y z))))
;;; call: (ctak 18 12 6)